The objective of this investigation is to use non-invasive, state-of-the-art diagnostic techniques to measure periodontal disease destruction, and model periodontal disease progression over time. Currently, periodontitis is thought to occur in bursts followed by variable length periods of remission. This model is based on relatively crude clinical measurements as well as on limited analytical methods. In the investigation proposed here, digital subtraction radiography and an electronic periodontal probe capable of attachment level measurement relative to the cementoenamel junction will be used to measure bone loss and attachment loss, respectively. The use of these nearly continuous measures of attachment and bone loss will allow detection of small amounts of disease progression, provide data to be used in modeling of the disease process over time, and provide excellent sensitivity for assessing the success of treatment protocols. Forty-two patients will be studied for 18 months. Examinations using electronic periodontal probing at one-month intervals and quantitative radiology at 4-month intervals will be performed. These data will be used to determine sites of periodontal disease progression. Multiple models of periodontal disease progression will be developed from the data collected. The utilization of advanced diagnostics may allow for a more rational scientific and less subjective basis to the modeling of periodontal disease; thereby adding to the understanding of the pathophysiology of the periodontal diseases.